TransmitFile 一次又一次地发送相同的字节
TransmitFile sending the same bytes again and again
我正在使用 TransmitFile 函数,它的作用与我预期的不同。
最小示例:
#include <mswsock.h>
int main(void)
{
WSADATA wsa;
SOCKET ListenSocket, ClientSocket;
struct sockaddr_in server;
if (WSAStartup(MAKEWORD(2,2),&wsa) != 0)
return 1;
if ((ListenSocket = socket(AF_INET , SOCK_STREAM , 0 )) == INVALID_SOCKET)
return 2;
server.sin_family = AF_INET;
server.sin_addr.s_addr = INADDR_ANY;
server.sin_port = htons(1234);
if (bind(ListenSocket, (struct sockaddr *)&server, sizeof(server)) == SOCKET_ERROR)
return 3;
listen(ListenSocket, 1);
if ((ClientSocket = accept(ListenSocket, NULL, NULL)) == INVALID_SOCKET)
return 4;
HANDLE hFile = CreateFile("alphabet.txt", GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
do {
if (!TransmitFile(ClientSocket, hFile, 3, 0, NULL, NULL, 0))
return 5;
Sleep(1000);
} while (1);
}
使用 MinGW 构建:g++ main.cpp -lws2_32 -lmswsock
文件 alphabet.txt
必须存在并包含:
abcdefghijklmnopqrstuvwxyz
当我 运行 程序并连接(例如使用 PuTTY 或 netcat)到端口 1234 时,我得到:
abcdefdefdefdefdef
我预计:
abcdefghijklmnopqr
使用您的确切代码,我能够重现该问题。在每次循环迭代中使用 SetFilePointer()
,我可以看到文件位置在第一次发送后按预期前进到偏移量 3,但在后续发送时从未超过偏移量 3,因此相同的 3 个字节被重新传输超过。为什么会这样,我不知道。
通过将 OVERLAPPED
结构传递给 TransmitFile()
(根据 documentation:
,是否在 CreateFile()
上指定 FILE_FLAG_OVERLAPPED
没有区别)
You can use the lpOverlapped
parameter to specify a 64-bit offset within the file at which to start the file data transfer by setting the Offset
and OffsetHigh
member of the OVERLAPPED
structure.
尝试这样的事情:
#include <mswsock.h>
int main(void)
{
WSADATA wsa;
SOCKET ListenSocket, ClientSocket;
struct sockaddr_in server = {};
HANDLE hFile;
if (WSAStartup(MAKEWORD(2,2), &wsa) != 0)
return 1;
if ((ListenSocket = socket(AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET)
return 2;
server.sin_family = AF_INET;
server.sin_addr.s_addr = INADDR_ANY;
server.sin_port = htons(1234);
if (bind(ListenSocket, (struct sockaddr *)&server, sizeof(server)) == SOCKET_ERROR)
return 3;
if (listen(ListenSocket, 1) == SOCKET_ERROR)
return 4;
if ((ClientSocket = accept(ListenSocket, NULL, NULL)) == INVALID_SOCKET)
return 5;
if ((hFile = CreateFileA("alphabet.txt", GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL)) == INVALID_HANDLE_VALUE)
return 6;
ULARGE_INTEGER ul;
ul.LowPart = GetFileSize(hFile, &ul.HighPart);
if ((ul.LowPart == INVALID_FILE_SIZE) && (GetLastError() != 0))
return 7;
OVERLAPPED ov = {};
ov.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
if (!ov.hEvent)
return 8;
unsigned __int64 uiPos = 0;
unsigned __int64 uiRemaining = ul.QuadPart;
while (uiRemaining > 0)
{
ul.QuadPart = uiPos;
ov.Offset = ul.LowPart;
ov.OffsetHigh = ul.HighPart;
DWORD dwNumToSend = (uiRemaining >= 3) ? 3 : (DWORD)uiRemaining;
if (!TransmitFile(ClientSocket, hFile, dwNumToSend, 0, &ov, NULL, 0))
{
if ((GetLastError() != ERROR_IO_PENDING) && (WSAGetLastError() != WSA_IO_PENDING))
break;
WaitForSingleObject(ov.hEvent, INFINITE);
}
uiPos += dwNumToSend;
uiRemaining -= dwNumToSend;
Sleep(1000);
}
closesocket(ClientSocket);
CloseHandle(ov.hEvent);
CloseHandle(hFile);
return 0;
}
或者,我没有使用 OVERLAPPED
,而是通过在每次发送后手动推进文件位置来使代码正常工作,再次根据文档:
If lpOverlapped
is a NULL pointer, the transmission of data always starts at the current byte offset in the file.
#include <mswsock.h>
int main(void)
{
WSADATA wsa;
SOCKET ListenSocket, ClientSocket;
struct sockaddr_in server = {};
HANDLE hFile;
if (WSAStartup(MAKEWORD(2,2), &wsa) != 0)
return 1;
if ((ListenSocket = socket(AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET)
return 2;
server.sin_family = AF_INET;
server.sin_addr.s_addr = INADDR_ANY;
server.sin_port = htons(1234);
if (bind(ListenSocket, (struct sockaddr *)&server, sizeof(server)) == SOCKET_ERROR)
return 3;
if (listen(ListenSocket, 1) == SOCKET_ERROR)
return 4;
if ((ClientSocket = accept(ListenSocket, NULL, NULL)) == INVALID_SOCKET)
return 5;
if ((hFile = CreateFileA("alphabet.txt", GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL)) == INVALID_HANDLE_VALUE)
return 6;
ULARGE_INTEGER ul;
ul.LowPart = GetFileSize(hFile, &ul.HighPart);
if ((ul.LowPart == INVALID_FILE_SIZE) && (GetLastError() != 0))
return 7;
unsigned __int64 uiPos = 0;
unsigned __int64 uiRemaining = ul.QuadPart;
while (uiRemaining > 0)
{
ul.QuadPart = uiPos;
if ((SetFilePointer(hFile, (LONG)ul.LowPart, (PLONG)&ul.HighPart, FILE_BEGIN) == INVALID_SET_FILE_POINTER) && (GetLastError() != 0))
break;
DWORD dwNumToSend = (uiRemaining >= 3) ? 3 : (DWORD)uiRemaining;
if (!TransmitFile(ClientSocket, hFile, dwNumToSend, 0, NULL, NULL, 0))
break;
uiPos += dwNumToSend;
uiRemaining -= dwNumToSend;
Sleep(1000);
}
closesocket(ClientSocket);
CloseHandle(hFile);
return 0;
}
我正在使用 TransmitFile 函数,它的作用与我预期的不同。
最小示例:
#include <mswsock.h>
int main(void)
{
WSADATA wsa;
SOCKET ListenSocket, ClientSocket;
struct sockaddr_in server;
if (WSAStartup(MAKEWORD(2,2),&wsa) != 0)
return 1;
if ((ListenSocket = socket(AF_INET , SOCK_STREAM , 0 )) == INVALID_SOCKET)
return 2;
server.sin_family = AF_INET;
server.sin_addr.s_addr = INADDR_ANY;
server.sin_port = htons(1234);
if (bind(ListenSocket, (struct sockaddr *)&server, sizeof(server)) == SOCKET_ERROR)
return 3;
listen(ListenSocket, 1);
if ((ClientSocket = accept(ListenSocket, NULL, NULL)) == INVALID_SOCKET)
return 4;
HANDLE hFile = CreateFile("alphabet.txt", GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
do {
if (!TransmitFile(ClientSocket, hFile, 3, 0, NULL, NULL, 0))
return 5;
Sleep(1000);
} while (1);
}
使用 MinGW 构建:g++ main.cpp -lws2_32 -lmswsock
文件 alphabet.txt
必须存在并包含:
abcdefghijklmnopqrstuvwxyz
当我 运行 程序并连接(例如使用 PuTTY 或 netcat)到端口 1234 时,我得到:
abcdefdefdefdefdef
我预计:
abcdefghijklmnopqr
使用您的确切代码,我能够重现该问题。在每次循环迭代中使用 SetFilePointer()
,我可以看到文件位置在第一次发送后按预期前进到偏移量 3,但在后续发送时从未超过偏移量 3,因此相同的 3 个字节被重新传输超过。为什么会这样,我不知道。
通过将 OVERLAPPED
结构传递给 TransmitFile()
(根据 documentation:
CreateFile()
上指定 FILE_FLAG_OVERLAPPED
没有区别)
You can use the
lpOverlapped
parameter to specify a 64-bit offset within the file at which to start the file data transfer by setting theOffset
andOffsetHigh
member of theOVERLAPPED
structure.
尝试这样的事情:
#include <mswsock.h>
int main(void)
{
WSADATA wsa;
SOCKET ListenSocket, ClientSocket;
struct sockaddr_in server = {};
HANDLE hFile;
if (WSAStartup(MAKEWORD(2,2), &wsa) != 0)
return 1;
if ((ListenSocket = socket(AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET)
return 2;
server.sin_family = AF_INET;
server.sin_addr.s_addr = INADDR_ANY;
server.sin_port = htons(1234);
if (bind(ListenSocket, (struct sockaddr *)&server, sizeof(server)) == SOCKET_ERROR)
return 3;
if (listen(ListenSocket, 1) == SOCKET_ERROR)
return 4;
if ((ClientSocket = accept(ListenSocket, NULL, NULL)) == INVALID_SOCKET)
return 5;
if ((hFile = CreateFileA("alphabet.txt", GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL)) == INVALID_HANDLE_VALUE)
return 6;
ULARGE_INTEGER ul;
ul.LowPart = GetFileSize(hFile, &ul.HighPart);
if ((ul.LowPart == INVALID_FILE_SIZE) && (GetLastError() != 0))
return 7;
OVERLAPPED ov = {};
ov.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
if (!ov.hEvent)
return 8;
unsigned __int64 uiPos = 0;
unsigned __int64 uiRemaining = ul.QuadPart;
while (uiRemaining > 0)
{
ul.QuadPart = uiPos;
ov.Offset = ul.LowPart;
ov.OffsetHigh = ul.HighPart;
DWORD dwNumToSend = (uiRemaining >= 3) ? 3 : (DWORD)uiRemaining;
if (!TransmitFile(ClientSocket, hFile, dwNumToSend, 0, &ov, NULL, 0))
{
if ((GetLastError() != ERROR_IO_PENDING) && (WSAGetLastError() != WSA_IO_PENDING))
break;
WaitForSingleObject(ov.hEvent, INFINITE);
}
uiPos += dwNumToSend;
uiRemaining -= dwNumToSend;
Sleep(1000);
}
closesocket(ClientSocket);
CloseHandle(ov.hEvent);
CloseHandle(hFile);
return 0;
}
或者,我没有使用 OVERLAPPED
,而是通过在每次发送后手动推进文件位置来使代码正常工作,再次根据文档:
If
lpOverlapped
is a NULL pointer, the transmission of data always starts at the current byte offset in the file.
#include <mswsock.h>
int main(void)
{
WSADATA wsa;
SOCKET ListenSocket, ClientSocket;
struct sockaddr_in server = {};
HANDLE hFile;
if (WSAStartup(MAKEWORD(2,2), &wsa) != 0)
return 1;
if ((ListenSocket = socket(AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET)
return 2;
server.sin_family = AF_INET;
server.sin_addr.s_addr = INADDR_ANY;
server.sin_port = htons(1234);
if (bind(ListenSocket, (struct sockaddr *)&server, sizeof(server)) == SOCKET_ERROR)
return 3;
if (listen(ListenSocket, 1) == SOCKET_ERROR)
return 4;
if ((ClientSocket = accept(ListenSocket, NULL, NULL)) == INVALID_SOCKET)
return 5;
if ((hFile = CreateFileA("alphabet.txt", GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL)) == INVALID_HANDLE_VALUE)
return 6;
ULARGE_INTEGER ul;
ul.LowPart = GetFileSize(hFile, &ul.HighPart);
if ((ul.LowPart == INVALID_FILE_SIZE) && (GetLastError() != 0))
return 7;
unsigned __int64 uiPos = 0;
unsigned __int64 uiRemaining = ul.QuadPart;
while (uiRemaining > 0)
{
ul.QuadPart = uiPos;
if ((SetFilePointer(hFile, (LONG)ul.LowPart, (PLONG)&ul.HighPart, FILE_BEGIN) == INVALID_SET_FILE_POINTER) && (GetLastError() != 0))
break;
DWORD dwNumToSend = (uiRemaining >= 3) ? 3 : (DWORD)uiRemaining;
if (!TransmitFile(ClientSocket, hFile, dwNumToSend, 0, NULL, NULL, 0))
break;
uiPos += dwNumToSend;
uiRemaining -= dwNumToSend;
Sleep(1000);
}
closesocket(ClientSocket);
CloseHandle(hFile);
return 0;
}